JD 300, 74/75? fuel line issue??

[Mista Mota]

Hey everyone

i just recently bought a 74/75 300. i'm not sure on the year exactly as from the research i have done says a 74 has a metal tank... where mine has a plastic/poly tank...

The sled itself is actually in really decent body shape from sitting in the barn for 20 years. The guy i bought it off of said he had not run it in at least 20 years... I cleaned out the gas tank, replaced both lines from the tank to the carb and replaced the vacuum hose to the block.
I also put in a new carb kit. now this is where the problem lies.. I filled the line as best as i could with fuel with a turkey baster, and shot a few sprays of fuel into the carb, it started up perfect on the second pull it sounded great and then died out as it would not continue to suck fuel from the line....

where do i go next to troubleshoot this?
is the carb not operating right? (how would one tell)

thanks in advance
Jeff

[JDT]

Replace the crank seals before you do anything else.

[Steven Rempel]

Yes crank seals. What carb do you have? did you replace the lines and pick up in the tank, if someone changed the tank back to metal what else might not be right?

[Matt]

If it's manufactured in 74 (75 model year) then the poly tank is correct. My question was going to be the same as Steven, did you put in a new pickup line/check valve in the tank?

[Mista Mota]

It has the walboro carb on it. i took it over to my buddies place and we put it on his old sled and it seemed to work fine.

Steven, Matt I have replaced all three lines the vacuum line going to the block, the pickup line from the tank through to the valve and from the valve to the carb, and i replaced the return line back to the check valve

i did not replace the valve as to me anyway it seemed in good condition... it wasn't rusted and fuel flows through it

i have yet to goto the parts store and grab all the parts i need, maybe this weekend if i have time, but probably next weekend

[jep_800]

Does the check ball rattle on the pickup check valve? If all lines are replaced, including the impulse line which is what transmits your crankcase pressure to "pump" fuel in the Walbro Carb, it should work. Did you get the correct line attached on the carb? In other words, the pickup line to the fuel fitting, and the fuel line that runs from the fuel fitting to the carb needs to be on the center fuel port on the bottom of the carb plate. The one closer to the side is the return line... I've seen these switched before, and in that case the carb will be sucking air instead of fuel. The diaphrams & gaskets that go into the Walbro are a process that needs to be correct for it to work. For example, if you turned the metering diaphragm upside down, it's not going to press the metering lever. But it sounds like you may have tested it on another sled with success?

The earlier points are correct too about the crank seals. It will not have the correct pressure, and you will eventually burn the engine down if they are not replaced.

Keep digging, the answer's in there somewhere.

JP

[Mista Mota]

hey guys, sorry for the long absence. got swamped with work and husbandly duties

I tested the carb again on a different sled and it seems to work fine with that. so i'm thinking its not a carb problem. I had time to play with the engine a bit, so i put a compression tester on it.. 30/25 i'm no genius but i think that rather low as all my other sleds in the past were in the 100 to 135 range.

so i've taken off the primary clutch yesterday only to realize that i didn't get a engine gasket kit, so after a long night in the garage and way too many "pops" to drive out and get it the weekend task begins!!

i'll let you know next week how it turns out

[Mista Mota]

So, after taking off the primary, and exhaust manifold from the head. i've also taken off the heat shield around the cylinder heads.
my next step in rebuilding this engine would be taking off the electric starting gear thats attached to the cam. any tips to take this beast off? iv'e threaded some bolts to through eh smaller holes on the side in attempts to pull it off that way, but with no success.
also do i also take off the stator? or will the engine split without removing that

thanks
j

[Steven Rempel]

The ring gear comes off and there is a hub that is pressed on to the ring. have you removed the 4 screws holding the ring gear to the pressed on hub. after the ring gear is removed I use a puller with hardened bolts and a lot of heat with torch to heat up the ring gear hub and then add a bit more pulling pressure the the puller and heat more. If this is the first time that the ring gear hub has been off in a long time it may take a few heat and cool cycles to get it off. dont worries about the heat and the old seal.

I have busted at least 6 set of puller bolts so dont worry if that happens it will come off, but can be a real PITA.

Also take note of the distance on how far the ring gear hub is on, I would measure with a caliper, If I remember right its like 30 or 31 mm.

I can send pics if you need.

[Steven Rempel]

the stator will have to come off to split the case take and mark it with a good scratch the mark the timing. to help get you close after rebuild for the timing.

I would also recommend downloading a service manual in pdf this can really help alot with order of process and give great tip as well

[Mista Mota]

Thanks, I'll give it try

[Mista Mota]

so i gave up trying to pull that stupid thing off... so i cut it off. i don't really need electric start anyway...


i took off the seal cover only to find it badly broken/worn the cover i mean... anybody have one of these i get??

thanks

[Steven Rempel]

I am sure I have one , send me a pm with your info and I will get you a cost of shipping plus 5 for the part if that a route you might be interested in. I have lots of part for these motors fyi

[Mista Mota]

I'm still stumped with this thing

the sled engine runs great if I spray gas into the carb. but it still refuses to suck any gas from the tank. I'll post some pictures of lines and such tomorrow

[Matt]

You left us with half the story here, you mentioned low compression, you were working on getting to the crank seals. What work have you done?